Field of the Invention
The present invention relates to a radiation imaging apparatus and a radiation imaging system.
Description of the Related Art
There is known a radiation imaging apparatus that performs static image capturing such as radiography, and moving image capturing such as fluoroscopy. An image generated by the radiation imaging apparatus contains fixed pattern noise (to be referred to as FPN hereinafter) arising from variations of the capacity at the time of manufacturing and variations of the offset of a readout circuit. The FPN is removed from a radiation image by subtracting an FPN image generated by performing readout from pixels in a state in which they are not exposed to radiation, from a radiation image generated by performing readout from pixels in a state in which they are exposed to radiation. This method is called FPN correction. In Japanese Patent Laid-Open No. 7-250283, a radiation image and an FPN image are generated for every frame of fluoroscopy, and FPN correction is performed. However, it is difficult to increase the frame rate by this method because an FPN image is generated for every frame. In Japanese Patent Laid-Open No. 2003-190126, therefore, an FPN image is generated before the start of fluoroscopy, and FPN correction of a radiation image of each frame is performed using the FPN image generated in advance.